Sulfonic Acid-Catalyzed Autoxidative Carbon-Carbon Coupling Reaction under Elevated Partial Pressure of Oxygen

Abstract

An aerobic organocatalytic oxidative CC bond formation reaction of benzylic CH bonds with various C-nucleophiles is described. The coupling reaction proceeds by simply stirring the substrates under elevated partial pressure of oxygen in the presence of a sulfonic acid catalyst at room temperature. Elevation of the pressure enables the reaction of a broad scope of nucleophile substrates otherwise showing poor reactivity at ambient pressure. The benzylic CH bonds of xanthene, acridanes, isochromane and related heterocycles could be functionalized with nucleophiles including ketones, 1,3-dicarbonyl compounds and aldehydes. Electron-rich arenes could be utilized as nucleophiles at elevated temperatures. The reactions are believed to proceed via autoxidation of the benzylic CH bonds to the hydroperoxides and subsequent nucleophilic substitution catalyzed by sulfonic acids.